PROJECT SUMMARY The overall objective of this proposal is to determine if individuals with patellofemoral (knee cap) pain (PFP) have features similar to knee osteoarthritis (OA). PFP is a common chronic problem, especially in active, young, adult females, that can lead to increased body mass index and physical inactivity. These changes may contribute to more prevalent problems like obesity, diabetes, and hypertension. PFP also may lead to knee OA, another source of physical inactivity. X-rays are typically taken to identify knee OA; yet cartilage breakdown may not necessarily become evident on imaging for years. Cartilage biomarkers found in urine and/or blood samples can detect tissue breakdown sooner. Moreover, younger individuals with PFP do not necessarily have evident cartilage changes on x-ray. However, we believe that elevated biomarkers are present. To date, researchers have not examined biomarkers in these patients. The aim of this study is two-fold. The primary aim is to compare a cluster of biomarkers between young, adult females with PFP to age-matched controls. Only females will be assessed due to naturally-occurring biomarker differences between males and females. Methods used for this aim will be collecting and analyzing urine and blood samples for a cluster of biomarkers. The second aim is to determine the effect that patella (knee cap) alignment and altered lower extremity movement (kinematics) patterns have on biomarkers in those with and without PFP. We believe that poor patella alignment and/or altered kinematics can lead to patella stress, pain, and elevated biomarkers. We will measure patella alignment using ultrasound (sonography) and kinematics using motion analysis. This analysis will compare biomarkers between females with and without PFP based on patella alignment and kinematics. Understanding the effect of patella alignment and kinematics will provide important information on treatments strategies used to treat this patient population. This study will support the mission of the National Institute of Aging, understanding ?mechanisms associated with normal aging pathologies.? Historically, PFP has been considered a self-limiting condition. However, emerging evidence suggests that it is an ongoing pathological process. Minimal, if any, research has been directed to understanding the potential long-term impact that PFP can have on bone health. We believe that this study will provide an initial step toward improving our understanding of potential long-term consequences associated with a common knee problem.